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National Dam Safety Program and Hydrology Needs
Advisory Committee on Water Information (ACWI) Subcommittee on Hydrology (SOH)
James Demby, P.E. – FEMAEd Beadenkopf, P.E., CFM – URS
April 22. 2013
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Agenda
� FEMA and the National Dam Safety Program
� New FEMA Tools to Enhance Dam Safety
� Existing Hydrologic Practices
� Developing Hydrologic Practices
� Hydrologic Needs
� Discussion
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FEMA and the National Dam Safety Program
FEMA provides leadership to the National Dam Safety Program to support the efforts of the state and federal agency partners through collaboration to continuously improve dam safety
� National Dam Safety Program Vision
“The benefits and risks of dams are understood and risks are
managed to improve public safety, economic strength, national
security, and to sustain the environment.”
� National Dam Safety Program Mission
“Reduce risks to life, property and the environment from dam failure
by guiding public policy and leveraging industry best practices across
the dam safety community.”
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FEMA and the Dam Safety Program
Key FEMA strategies to realize the vision and missionand to reduce the risk to the American public from dam failures
� Promote community and regional resilience
� Increase awareness of dams by the downstream public
� Increase the number and updates of EAPs
� Assess the risk associated with dams
� Increase inspections of dams
� Increase the number of stakeholders trained about dam safety
� Expand the research program
� Translate research products into training
� Achieve the participation of all states in the program
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FEMA and the National Dam Safety Program
Collaboration among federal agencies, states, and dam owners is the key to increasing dam safety
� FEMA is transferring the coordination of state grants under the
National Dam Safety Program to the FEMA Regional Offices to
increase the working relationship between Risk MAP and dam safety
� FEMA is partnering with federal agencies to develop new tools for
increasing dam safety and the evaluation of the consequences of
potential dam failures
� FEMA is developing new products in collaboration with the Risk MAP
program to support local government’s communication of the
potential flood risk related to dam failures and to develop mitigation
actions to reduce the risk
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New FEMA tools to enhance dam safety
An increasing role for Risk MAP� Identify the flood hazard associated with potential dam failure incidents
� Provide flood risk data to local governments for their use in preforming dam
breach consequence studies and for hazard mitigation
� Provide tools for local governments to create risk communication products to
inform the public the risk living downstream of dams
� FEMA non-regulatory products for dams provide dam breach flood zone depth-velocity HAZUS compatible datasets for risk communication and for use in consequence studies and hazard mitigation planning
� 2012 NFIP reauthorization authorizes FEMA in coordination with a Technical Advisory Committee the provision to identify,
review, update, maintain, and publish NFIP rate maps with
respect to…areas that could be inundated as a result of the
failure of a levee, dam, or other flood control structure…
� By identifying the flood hazards related to living downstream of dams, new development may be avoided that results in “hazard creep”
Risk communication map showing the Special Flood Hazard Area superimposed on a dam breach flood inundation zone
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Traditional products are
regulatory and subject to statutory
due-process requirements
Risk MAP products are non-
regulatory and are not subject to
statutory due-process requirements
Non regulatory products overview
DFIRM Database
Traditional Regulatory Products Non-Regulatory Products
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Non-Regulatory Datasets – Dams
� Leverages existing analysis from dam
safety officials
� Flexible depending on varying state
regulations & methods
� Datasets proposed:
� Basic dam characteristics
� Upstream inundation areas delineated
� Downstream inundation areas delineated
� Assorted depth and analysis grids (depth, velocity, arrival time)
� Easements & critical facilities
� Flood risk assessments
� Additional Areas of Mitigation Interest categories
� Data would be used to communicate
risks & promote mitigation
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New FEMA Tools to enhance dam safety
� Provides guidance to States to model dam breach
zones and Emergency Action Plans (EAP’s) consistently
throughout the US
� Presents a tiered dam breach study process that
introduces simplified dam breach modeling methodology
as a tool to increase the number of dam breach studies
and EAP’s
� Provides standards for GIS-based dam breach model
file naming and EAP map production so Risk MAP can
leverage dam breach models and maps for the non-
regulatory products
Federal Guidelines for Inundation Mapping of Flood Risks Associated with Dam Incidents and Failures Guidance for State Regulators
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New FEMA Tools to enhance dam safety & RiskMAP
GEOSPATIAL DAM BREACH RAPID EAP, CONSEQUENCES AND HAZARDS
(GEODAM-BREACH) TOOLSET.� Developed in conjunction with the “Dam
Breach Guidelines” to also support Risk MAP
� Provides a GIS-based simplified dam breach
modeling and mapping capability based on the
NWS SMPDBK program in use at River
Forecast Centers
� Provides a capability to convert dam breach
model results to standard Risk MAP non-
regulatory datasets
� Provides a loss of life tool
� Provides semi-automated EAP report and map
generation linked to the dam breach model
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GeoDam-BREACH Toolset Functionality
Simplified dam breach modeling
Simplified dam breach modeling
Depth: 7.8 FTDepth: 7.8 FT
Risk MAP flood depth grid datasets
Risk MAP flood depth grid datasets
Risk MAP flood arrival time dataset
Risk MAP flood arrival time dataset
The RESIDUAL FLOOD RISK MAP is not currently a FEMA non-regulatory
product. It includes the regulatory 100-year floodplain overlaid with the
dam breach inundation zone
The RESIDUAL FLOOD RISK MAP is not currently a FEMA non-regulatory
product. It includes the regulatory 100-year floodplain overlaid with the
dam breach inundation zone
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EAP Map Production Tools
� Tools for map paneling to
standard sizes
� Standard map collar
� Automatically retrieves data
from the dam breach model
� Annotation tools
GeoDam-BREACH Toolset Functionality
EAP semi-automated report
� Provides simple data entry that populates a
editable Microsoft Word document
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New FEMA Tools to enhance dam safety
� Flexible guidance intended for both federal and state agencies to update guidelines at their discretion
according to their varied goals and resources
� No Difference between new and existing dams
� The application of less stringent criteria for existing
“grandfathered” dams is discouraged.
� Eliminate Use of “emergency spillway terminology”
� References to through flow through “emergency
spillways often leads to misconception by the public
that an emergency condition exists at a dam when the
dam is functioning as designed
Selecting and Accommodating Inflow Design Floods for Dams
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New FEMA Tools to enhance dam safety
� Flexible guidance intended for both federal and state agencies to update guidelines at their discretion
according to their varied goals and resources
� Eliminate Size in dam classification
� Recommend that dam be classified according to
hazard potential or adverse consequences should the
dam fail.
� Any classification system based on size (height or
storage volume) should be discontinued.
� Eliminate use of percentage of PMF
� Recommend that the practice of using composite
criteria and arbitrary percentages of hydrologic events
be discontinued.
Selecting and Accommodating Inflow Design Floods for Dams
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Existing Hydrologic Practices
Prescriptive event-based hydrology
� In practice for the vast majority of 88,000+ regulated dams
� Hydrology based on a prescriptive frequency event (typically a 50-, 100- yr. etc.) and/or percentage (fraction) of the PMF
� States regulate hazard potential classifications based on the downstream consequences of a dam failure which in turn establishes the inflow design flood (IDF) event for design. Many states allow a risk-based reduction in the IDF
� The current state of the practice requires the development of a hydrograph for the extreme events for dam breach modeling and watershed routing
Hydrologic Issues
� Unavailability of rainfall-runoff data for extreme events for model validation
� Perceived issues with the age of the NWS HMR PMP publications
� Uneven selection of temporal and spatial rainfall distributions for extreme events
� Lack of consensus and guidance for incorporating future condition hydrology such as potential watershed development and climate change
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Existing Hydrologic Practices
Risk-based design� Established to identify optimal design and stretch limited funding
� Requires the hydrologic evaluation of a range of extreme events and the
associated consequences of potential dam failure
� Many States allow the use of incremental damage assessments
Issues� Same hydrologic issues as noted on the previous slide
� Increasing importance of a detailed hydraulic model (unsteady and /or 2D
model of downstream areas
“The inflow design flood selected using incremental consequence analysis is the flood above which there is a negligible increase in downstream water surface elevation, velocity, and/or consequences due to failure of the dam when compared to the same flood without dam failure”.
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Developing Hydrologic Practices
Probabilistic Flood Hazard Assessments (PFHA)� Developing risk assessment methodology pioneered by USACE, USBR,
NRC, and FERC to evaluate their dam inventory
� Requires the probabilistic hydrologic evaluation of extreme events up to
PMF and beyond
� Requires highly specialized technical expertise and effort
� Hydrologic evaluations for extreme events involves multiple methods
including statistical evaluation of extreme flood records, watershed
modeling and paleo hydrology
Hydrologic Issues� Highly technical and costly limiting its use to select high value dams
� Technical expertise does not exist throughout the dam safety community
� Procedures are in development stage for repeatability
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Hydrologic Needs
� An internet accessible metadata identifying the availability of extreme rainfall and runoff data with links to sites for downloading propriety (for fee) and public data
� Updated guidance on frequency-based hydrologic evaluations of extreme events
� Updated PMP data and user guidance. Perhaps as the expansion of state specific updates to the NWS HMR publications to reflect current historical extremes and advancements in meteorology since the HMR publications were completed. Guidance for base flow and rainfall temporal and spatial distributions.
� Federal guidance on the incorporation of future conditions hydrology involving projected watershed development
� Continued research and guidance on the appropriate inclusion of climate change on hydrologic evaluations
� Agreement among the ICODS agencies on how the prescriptive event-based approach currently in practice throughout the US coexists with the developing probabilistic risk-based methodology
� Development of guidance and training to the dam safety community on the hydrologic principles of probabilistic considerations in dam design and dam
safety
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Discussion
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